This invention relates to the art of programmable function controllers and more particularly to a controller specifically applicable for use in waveform generation wherein an analog signal is generated based on digitized representations of the waveform.
Circuits known in the art for use in conjunction with waveform generation include the U.S. Pat. No. 3,386,039 to J. A. Naive, and 3,689,914 to Butler. The former patent presents an analog system for use in producing waveforms. The latter patent employs a digital approach wherein an accumulator stores digital signals which are then applied to a digital-to-analog converter to provide an analog output signal.
Later versions of circuitry for generating waveforms have included computer assistance An example is found in the U.S. Pat. No. 3,694,632 to Bloomer, Bloomer employs a matrix of digital differential analyzer integrators in conjunction with a computer. The computer interconnects the integrators within a matrix for generating digital patterns which are then converted by a digital-to-analog converter.
The U.S. Pat. No. 4,168,527 to Winkler, discloses a processor controlled waveform generator wherein a plurality of digitized waveforms are stored as digitized words in a memory. A processor controls the supply of these digitized words to a register which serves to minimize skewing effects as the words are then supplied into an analog-to-digital converter.
Another waveform generator known in the prior art takes the form of that available from Wavetek of San Diego, Calif. and known as their Model 175 Arbitrary Waveform Generator. This is described and illustrated in their instruction manual, Instrument Release D-2, 1980, Manual Revision, May, 1980. The Model 175 waveform generator employs a memory that stores digitized waveforms and is on-line with a data processor. The data processor selects a digitized waveform from the memory. Each data word obtained from the memory is supplied to a digital-to-analog converter for generating the analog version of the waveform. Also, the memory is addressed under processor control from a START address and this continues to a STOP address defining a block of locations containing digitized waveforms. A processor may select a continuous mode of operation or a trigger mode of operation and the processor may control the number of cycles of generating waveforms.
In both the Winkler patent as well as in the Wavetek Model 175, the processor is continuously on line with the waveform generator circuitry for controlling the operation of interrogating the memory and outputting digitized data points. Consequently, the circuitry is limited to use with a specific processor employed in an on line operation.